Adding a Bedoom or Office? How Much Does a Room Addition Cost?

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Whether you want to raise the roof of your house to transform your attic into a second-story living space or expand the footprint of your cramped and cluttered kitchen, an experienced professional can help you build the home addition you’ve been daydreaming of.

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Home Addition Cost

There are many options to choose from when planning to add extra space to your home. You can add a bathroom, master bedroom suite, build an in-law apartment, build a detached garage, family room, or add a second floor.

Building an addition increases the square footage, which adds value to a home. Each type of addition project has estimated prices primarily based on the size that we’ll cover below.

Home Addition Cost Per Square Foot

A home addition costs between $86 and $208 per square foot, with most spending $128 per square foot on average. The final cost depends on if your building-up or building-out, labor costs, and the quality of materials used.

 Home Addition Cost Per Square Foot   Quality Cost

Home Addition Cost Per Square Foot
Quality Cost Per Square Foot
Basic $86
Average $128
Luxury $208

On average, the addition consists of a basic room with necessary electrical wiring and little to no plumbing. Features such as bedrooms and bathrooms with luxury fixtures start raising that square footage price. Every door, window, and wall adds to the price. The more luxurious the design of the addition, like a chef’s gourmet kitchen with smart appliances and heavier electrical needs, the higher the price—at $400 per square foot or higher.

Home Addition Cost Calculator

Calculating by square footage is quite accurate when trying to assess the final cost of an addition. An average 300 square foot addition costs $25,800 to $62,400 while a 400 square foot addition runs $34,400 to $83,200. Costs below are figured at $86 and $208 per square foot to show the most basic cost to the highest.

 Home Addition Cost Estimator   Square Feet Averag

Home Addition Cost Estimator
Square Feet Average Cost
200 $17,200 – $41,600
250 $21,500 – $52,000
300 $25,800 – $62,400
400 $34,400 – $83,200
500 $43,000 – $104,000
600 $51,600 – $124,800
800 $68,800 – $166,400
1,000 $86,000 – $208,000

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Cost to Design a Home Addition

Do not overlook the designing aspect of the addition because it is an important step. Your addition must match the details of your home inside and out to be seamless and to get the most value. Designing also makes the most of the space, so more is done with less square footage.

The general rule of thumb when it comes to the cost of designing a home addition is for the designs to cost between 10% and 17% of the final costs. So, for a 240 sq.ft addition costing $55,000, you pay between $5,500 and $9,350. This varies, depending on the designer and detail of the plans.

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Curb Appeal Of A Home Addition

When designing a home addition, whether its its just a sun room or a two-storie master suite or an in-law apartment, its important to consider how the addition will look attached to the main home.

The last thing you want is for the addition to seem like it was hastily tacked on to the house and now it sticks out like a sore thumb.

Ideally, an addition should look like an organic extension of the house, where the flow from the old space to the new feels very natural. This requires professional architectural planning and design.

Its also important to carefully select your siding and roofing materials, so that they match and complement the siding and roof of your original home.

While you may not care what your addition looks like on the outside, this may become a stumbling block if you ever decide to sell your home.

Prospective buyers will love the expanded foot print of your house, but they may have a major problem if the addition really looks out of place.

A new design trend that has been growing in popularity is to build a modern addition together with a classic architectural style home.

Modern additions usually have flat roofs, oversized windows and make use of engineered wood or fiber cement siding materials.

How a home addition calculator works

A home addition calculator typically asks you to input what type of project you’re working on and the size of your addition. Then it will ask you for your ZIP code or city, using that information to find the typical per square foot or overall cost from contractors in your location. Calculators will generally include fixed costs such as permitting as well as the type of building materials and extensiveness of electrical, plumbing or roofing needed.

Once you have an estimate, some calculator services can even connect you with contractors in your area.

Home Extension Cost by Type

There are many other ways to add to your home to expand your living space, and not all create complete rooms. Extensions can be a way for you to gain valuable square footage and living space, without all the expense of a full addition. You can create an extension in many ways, from simple bump outs, balconies, and dormers to in-law apartments. An extension can come in a wide range of sizes and costs and have a variety of appearances.

Extension TypeAverage Cost (Labor Included)Bump Ou

Extension TypeAverage Cost (Labor Included)
Bump Out$4,000 – $9,000
Dormer$4,000 – $9,000
Balcony$4,000 – $9,000
Greenhouse$5,000 – $20,000
Porch$12,000 – $30,000
Cantilever$15,000 – $25,000
Modular$20,000 – $30,000
Garage$22,000 – $43,000
In-Law$60,000 – $100,000

Bump Out Addition Cost

Bump out additions typically cost between $4,000 and $9,000. As you will need no foundation work, you can save about 15 percent compared with a conventional addition. A bump out is a small extension of an existing room. It adds square footage but at a much lower cost. Because this is not a full room, the costs are considerably lower. Bump outs are most common on the first floor, but they can be done on the second floor as well. They are good for adding small spaces like laundry rooms and adding storage to a room.

Dormer Addition Cost

Dormer additions range from $4,000 to $9,000 on average. A dormer is a roof extension with a window. It adds extra space to a low-ceilinged room like an attic space. On the inside, the dormer can create a window seat with added storage. If your ceilings are high enough, it can also create additional standing room. Dormers are also attractive additions on the exterior since it changes the profile of your home and can make it look more attractive.

Balcony Addition Cost

Balcony additions average $4,000 to $9,000. A balcony is a small deck suspended off the side of the home and is usually a short and simple project. It is a nice way of updating your home’s exterior, while gaining usable outdoor space. If you do not have the room for a full deck or porch but want somewhere to sit outdoors, a balcony makes a lot of sense. They can come in many sizes and styles to complement all homes.

Greenhouse Addition Cost

Greenhouses typically cost between $5,000 and $20,000 on average. If you do a lot of gardening, add a greenhouse to your property. There are several different ways you can do this. You can add the greenhouse directly onto your existing home, creating a lean-to style structure. You can also make the greenhouse a completely separate structure of many different shapes and sizes elsewhere on your property. Each style has its own costs as well as pros and cons to consider.

Porch Addition Cost

Porch additions range from $12,000 to $30,000. Adding a porch boosts your home’s curb appeal and value while adding outdoor living space. Porches come in a wide range of sizes and styles. They can be small porticos at your entrance or enormous verandahs that wrap around the house. A porch can give you a lot of space for recreation and entertaining, while at the same time improving the appearance of your home.

Cantilever Addition Cost

Cantilevering an addition onto your home averages $15,000 to $25,000. If you want to add a room to the second floor of a home, extend the space by cantilevering it out over the lower floor. These spaces are not big, but the added support increases costs. The space below can be supported on posts, similar to a deck, or it can be supported by having the posts angle back to the house. They brace themselves against the house itself, so no actual ground space is taken.

Modular Room Addition Cost

Modular room additions cost between $20,000 and $30,000 on average. Modular building is less expensive than traditional because the room is factory-built, delivered, and added onto your existing home. The cost per square foot is lower, and the timeline is faster. Best of all, modular additions can be made in nearly any style, size, or configuration. So you can easily get one that seamlessly matches up with the rest of your home.

Garage Addition Cost

The cost of a garage addition ranges from $22,000 to $43,000 on average. Having an attached garage improves your home’s value and improves overall function as well. With an attached garage, your car is more secure and protected from the elements. Garages also offer a lot of storage and can also be used for a variety of other purposes. You can use your garage as a workshop, gym, or any number of other uses.

In-Law Addition Cost

An in-law addition has a cost range of $60,000 to $100,000, depending on the size. An in-law is a fully fitted small building or apartment that is either attached or detached from the rest of your home. Because they often contain kitchens and baths, their costs are higher than additions of a similar size without these features. In-laws can be a great way to have multi-generational families living together under one roof. They require a separate entrance from the main home, as well as other features that make them a stand-alone apartment.

Benefits of a Home Addition

It’s a toss-up to decide where to spend your hard-earned money sometimes. If buying a new house isn’t an option, but you need extra space, then doing a home addition is a great solution. Home addition costs are well spent when improving and expanding a home. Here are several popular reasons to add to your home that will get you excited for this project.

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More Space

This is likely the number one reason homeowners spend money on home additions. More space is a considerable benefit for growing families, holding large gatherings, or adding storage or living space. Adding only a few feet of space to a cramped bedroom can help couples regain their own space. Expanded living rooms offer more room for families and friends to gather for important events. More space allows for you to adhere to your lifestyle values.

Added Property Value

Many household construction projects increase your property value—the question is by how much. No project offers a dollar-for-dollar return, which is why it’s wise to avoid extravagant upgrades that won’t make a significant difference. However, some projects can boost your property value. A master suite addition returns 63 percent, a bathroom returns 53 percent, and a second-floor addition returns 65 percent. You could speak with a real estate agent or home appraiser to get an idea about which additions and features will best help your property value.

Added Luxury

If your bathroom is as small and basic as it gets, bumping out your bathroom could be a huge benefit that adds spacious luxury to an intimate area. Having a little extra room to take care of your personal needs is fast becoming necessary to appeal to future home buyers. Additionally, expanding a kitchen to add more appliances or counter space is another way to make a common living area appear more luxurious.

More Storage

Building a garage offers two immediate benefits: protection for your vehicles and extra storage space. If you already have a garage but still need extra storage space, bumping out a larger area for a laundry room and mudroom could be a perfect idea. With built-in cabinets and closets, you’ll have plenty of space to store outdoor items or seasonal clothing and bedding.

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Moving Alternative

Almost every homeowner dreads the moving process simply because of the tremendous hassle of packing, moving, and then unpacking your life’s possessions. There’s also the possibility that you cannot find a house that suits your needs in the area you specifically want to raise your family. Choosing to build an addition on your home solves all of those problems—if you have space—and it’s usually cheaper than buying a new house.

Obtaining a Permit

After you have determined an average cost by using a home addition calculator, consider obtaining a permit. Without debating whether permits are worth the additional cost, whether permits require other upgrades or whether your neighbors do work without a permit, consider the inherent problem on resale without a permit. Appraisers will most likely not include the upgrades or addition if there is no permit on file.

If you hire a general contractor, to save costs, the contractor might suggest you bypass the permit. Ask if the contractor will obtain a permit and insist on receiving a copy of the permit, including the completion certificate. Sellers of a home in Carmichael paid their contractor more than $100,000 to add a master suite.

They thought the contractor had obtained a permit. When we sold the house, the appraiser could not find a permit for the room addition, which resulted in a low appraisal. The sellers paid $8,000 to the county of Sacramento to obtain an as-built permit. Buyer’s lenders today expect to see a permit.

Factors That Drive Up Home Addition Cost

There are a number of factors that may significantly increase the total cost of an addition.

For example, if you are adding a new bathroom or a kitchen, you will need to install an entirely new plumbing system.

This will cost thousands of dollars. One way to save money on this is to connect to the existing plumbing system, if the addition design allows for it.

Another significant expenditure is hiring a mason to pour a level concrete floor, if you are planning to build a garage.

You should also budget at least $1,500-4,000+ extra to fix the landscaping around the new addition.

You will need to pull building permits for most of the construction and remodeling jobs. Each permit will be a few hundred dollars. Also, you may need to run special kinds of tests, such as soil testing, which may cost $1,000+

Keep in mind that if you do not hire a General Contractor to oversee the project and hire subcontractors, you will need to hire these pros yourself to complete specialized tasks. They may include a roofer, electrician, plumber, window installer, etc.

Lastly, the quality of materials you select will also make a great difference in the final cost.

Choosing custom, brand name, or luxury building materials can significantly drive up construction costs. Here, you need to carefully consider your total budget and what you are planning to achieve.

Sometimes, going for more expensive materials is justified because of their improved longevity and durability, as opposed to spending a lot more money just to have an upscale look.

For example installing a metal roof instead of asphalt shingles may cost $10,000-15,000 more, but will offer superior weather protection for the lifetime of your house.

Will My Home Addition Cost Be Worth It?

A home addition will certainly increase the value of your home, but don’t expect to receive a dollar-to-dollar return on your home addition cost investment.

According to, this is what you can expect to get back, should you sell your home:

  • Bathroom addition: 53%
  • Master suite: 63%
  • Full 2nd story: 65%

It’s still a good ROI, but not worth the money if you think of it solely in resale terms. Instead, build an addition that will enhance your home life, so you can enjoy it. You’ll get your money’s worth out of your home addition cost before you ever list your home.

But for future resale, it is always a good idea to consult with a local Realtor before proceeding with a home addition. Use UpNest’s free service to find one of the top real estate agents in your market. They can offer you guidance based on what local buyers expect in a home, so that you get top dollar for your addition, when you sell your home. 

UpNest is a no-cost service for home sellers and buyers to find the best real estate agents locally. The UpNest platform allows you to compare multiple agents in your area so you can compare reviews, commission rates, previous sales, and more.

Our agents have been carefully vetted and often offer competitive, lower than average commission rates to UpNest customers. There is no obligation to sign up with one of our Realtors, but when you can potentially save thousands on commission – why wouldn’t you? If you’re ready to get started, just enter your zipcode below!

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How much does a 20×20 addition cost?

This varies depending on factors like material prices, location, and cost of labor, but the average homewoner spends between $42,000 to $88,000 to add a 20×20 room addition, with an average cost of $65,000. Building a 20×20 room addition can give you the extra space you need in your house, and it’s a lot cheaper than buying a new home. Most homeowners spend from $42,000 to $88,000 to add a room of this size.

Is it cheaper to add on or build up? There is some debate on this question, but most believe that when building new construction, building up with a two-story home is cheaper than building out. When remodeling, building out with a one-story addition is cheaper than adding a second story to an existing dwelling.